Conventionally, carbon fiber composite materials have been used, for example, in airplane structures that require weight reduction.
As a method of monitoring resin hardening of a carbon fiber composite material, there is a method that uses an optical fiber having a grating sensor provided inside, as described in the Japanese Translation of PCT International Application, Publication NO. 2000-501176.
Generally, members such as carbon fiber composite materials are joined together by using fasteners such as rivets or bolts.
When joining members together, although it is optimal to use an adhesive from the viewpoints of weight reduction, working efficiency, etc., this requires the evaluation of bonding quality. The evaluation of bonding quality is conducted, for example, by way of ultrasonic testing after members are joined together by using an adhesive.